Powder supply system and powder supplying unit used in the system

ABSTRACT

A powder supply system including a powder replenishment device as a powder source, a suction device and a plurality of powder supply units connected in series. Each of the powder supply units sprinkles powders toward an object mounted on each processing device. An upstream end powder supply unit is fluidly connected to the powder replenishment device, and a downstream end powder supply unit is fluidly connected to the suction device. A suction force generated by the suction device sucks powders from the powder replenishment device through the powder supply units, and powders are successively accumulated in the powder supply units in the order from the upstream end powder supply unit to the downstream end powder supply unit. A powder sensor is provided between the rearmost powder supply unit and the suction device. If all powder supply units are filled with powders, residual powders are discharged out of the downstream end powder supply unit. If the sensor detects the powder, operation of the suction device and the powder replenishment device is stopped.

BACKGROUND OF THE INVENTION

The present invention relates to a powder supply system for supplyingpowder, and more specifically, to the powder supply system forreplenishing powder in a plurality of powder supply units.

Conventionally, a plurality of powder supply units for supplying powderat various stages along a production line have been provided atdifferent locations along the production line. For example, in aproduction line such as a line for producing bread, a plurality ofpowder supply units are provided each in association with eachprocessing device, so that powders in the powder supply unit aresprinkled on the surface of dough at the processing device.

According to a conventional powder supply system, a powder replenishmentdevice or a powder replenishment device having a pressure source hasbeen provided for supplying powder to each one of the plurality ofpowder supply units to replenish powder in the powder supply units. Theplurality of the powder supply units are connected to the powderreplenishment device by pipes arranged in parallel. Pressurized air fromthe pressure source is used to supply powder to the plurality of powdersupply units.

The pressure source generates a high pressure to create and air flow inthe pipes sufficient for moving the powder through the pipes. Therefore,the piping must be highly resistant to high pressure. Also, the portionswhere separate pipes are connected together need to be maintained with aproper seal. The configuration for maintaining the seal becomescomplicated to withstand the high pressure in the pipes.

Japanese Laid-Open Patent Application (Kokai) No. SHO-63-272720discloses a configuration for transporting powder using a flow of aircaused by suction force generated by a suction unit. Utilization of thenegative pressure can avoid problems attendant to the utilization ofhighly positive pressure.

However, in these conventional configurations for replenishing powderfrom the powder replenishment device to each of the plurality of powdersupply units, the plurality of powder supply units are connected inparallel with respect to the powder replenishment device whether theconfiguration is for supplying powder by pressurized air or by suctionof air. This parallel construction requires branch pipes fordistributing powder from the powder replenishment device to theindividual powder supply units. This complicates the piping arrangementfor transporting powder. Further, a switching valve for switchingtransport of powder to each of the powder supply units must be providedto each powder supply unit or to each branch pipe portion. This can makethe overall cost of piping expensive.

SUMMARY OF THE INVENTION

It is therefore, an object of the present invention to overcome theabove-described problems and to provide an improved powder supply systemhaving a simple structure without employment of the switching valve.

Another object of the present invention is to provide an improved powdersupply unit available for the powder supply system.

These and other objects of the present invention will be attained byproviding a powder supply system for supplying powders to a plurality ofprocessing devices including a powder replenishment device, a powdersuction device, a plurality of powder supply units, and a powder sensor.The powder replenishment device stores therein powders. The powdersuction device is adapted for suckingly discharging the powders in thepowder replenishment device. The plurality of powder supply units areconnected in series and are positioned between the powder replenishmentdevice and the powder suction device. The plurality of powder supplyunits include an upstream end powder supply unit and a downstream endpowder supply unit, each powder supply unit being provided for supplyingpowders to each processing device. Each powder supply unit includes anauxiliary tank, a powder inlet conduit, a powder outlet conduit, and apowder supplying portion. The auxiliary tank is adapted for temporarilystoring therein the powders. The powder inlet conduit is connected to anupper portion of the auxiliary tank for introducing powders into theauxiliary tank. The powder outlet conduit is connected to the upperportion of the auxiliary tank for discharging the powders from theauxiliary tank. The powder supplying portion is provided at a lowerportion of the auxiliary tank for supplying the powders conveyed fromthe auxiliary tank to each processing device. The inlet conduit of theupstream end auxiliary tank is connected to the powder replenishmentdevice and the outlet conduit of the downstream end auxiliary tank isconnected to the powder suction device. The powder suction device sucksthe powders in the powder replenishment device through the inletconduits and the outlet conduits and through the respective auxiliarytanks for successively and fully accumulating powders in the auxiliarytanks in the order from the upstream end auxiliary tank to thedownstream end auxiliary tank. The powder sensor is connected downstreamof the downstream end powder supply unit for detecting a fullaccumulation of the powders in all auxiliary tanks and for stoppingoperation of the powder replenishment device and the powder suctiondevice as a result of the powder detection.

In another aspect of the invention, there is provided a powder supplyunit connected to a powder source for supplying powders to a processingdevice, the powder supply unit including a powder reservoir, a powdersupplying portion, an auxiliary tank, a powder inlet conduit, a powderoutlet conduit, and a valve. The powder reservoir is adapted fortemporarily storing powders therein. The powder supplying portion isconnected between a lower end of the powder reservoir and the processingdevice. The auxiliary tank is connected to an upper end of the powderreservoir. The powder inlet conduit is connected to an upper portion ofthe auxiliary tank for introducing powders into the auxiliary tank. Thepowder outlet conduit is connected to the upper portion of the auxiliarytank for discharging the powders from the auxiliary tank. The valve isprovided at the lower portion of the auxiliary tank and movable betweena close position for accumulating the powders in the auxiliary tank andan open position for dropping the powders in the auxiliary tank into thepowder reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic view showing an overall configuration of a powdersupply system according to a first embodiment of the present invention;

FIG. 2 is a side view showing a powder supply unit according to thefirst embodiment of the present invention;

FIG. 3 is a front view partly in cross-section showing the powder supplyunit of FIG. 2;

FIG. 4 is a plan view showing the powder supply unit of FIG. 2;

FIG. 5 is a front view showing a cyclone classifier used in the systemshown in FIG. 1;

FIG. 6 is a cross-sectional side view showing a powder supply unitaccording to a second embodiment of the present invention; and

FIG. 7 is a front view showing the powder supply unit of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A powder supply system according to a first embodiment of the presentinvention will be described with reference to FIGS. 1 through 5.

FIG. 1 is a conceptional view showing a production line for producingbreads and other baked goods. Powder supply units 11A to 11C areprovided for supplying powder to respective processing devices along theproduction line. The production line includes a powder replenishmentdevice 13, for replenishing the powder to the powder supply units 11A to11C.

More specifically, the production line includes a dough supply machine1, a first stretcher 5, and a second stretcher 9 those disposed in thisorder from left to right as viewed in FIG. 1. A first conveyer belt 3 isdisposed to extend from an upstream side of the dough supplying machine1, under the dough supplying machine 1, and to the first stretcher 5.Also, a second conveyer belt 7 is disposed between the first stretcher 5and the second stretcher 9.

The dough supply machine 1 serves as a first processing device forsupplying dough, which serves as a material to be processed. The firstconveyer belt 3 is provided as a transport unit for transporting thedough from the dough supply machine 1 to the first stretcher 5, where asuccessive process is performed. The first stretcher 5 serves as asecond processing device and is disposed at the final transport positionof the first conveyer belt 3. The second conveyer belt 7 is disposed inconnection with the first stretcher 5 and is provided for transportingthe dough stretched out in the first stretcher 5 to the second stretcher9. The second stretcher 9 serves as a third processing device and isdisposed at the transport end of the second conveyer belt 7.

In other words, the production line is provided with a dough supplyingmachine 1 for supplying a material to be processed, a transport meansfor transporting the material from the dough supplying machine 1 to asuccessive process, and a second and third process machines forperforming appropriate processes on the material transported by thetransport means. The transport means and the second and third processmachines are appropriately disposed in the production line.

The powder supply units 11A, 11B, and 11C are disposed at a plurality oflocations as needed along the production line and are all connected inseries one after another along the production line via a connection pipe41. The powder supply units 11A to 11C serve as powder sprinkling units,for sprinkling powder for powdering the surface of dough to prevent thedough from sticking to components of the processing devices 1, 5, and 9.

The powder supply unit 11A is disposed upstream from the dough supplymachine 1 at the starting edge of the first conveyer belt 3. Because thepowder supply unit 11A is disposed furthest upstream of all the powderssupply units in the production line, the powder supply unit 11A willalternately be referred to as the upstream end powder supply unit 11ahereinafter.

The powder supply unit 11B is disposed at the end side of the firstconveyer belt 3, that is, at the position where the first conveyer belt3 finishes transporting the dough to the entrance to the first stretcher5. The powder supply unit 11B will alternately be referred to as themiddle powder supply unit 11B, hereinafter.

The powder supply unit 11C is disposed at the entrance to the secondstretcher 9, that is, at the end of the conveyor belt 7 where the doughis introduced into the second stretcher 9. Because the powder supplyunit 11C is disposed furthest downstream of all the powders supply unitsin the production line, the powder supply unit 11C will alternately bereferred to as the downstream end powder supply unit 11C, hereinafter.

As mentioned previously, the powder replenishment device 13 is providedfor supplying powder to the powder supply units 11A to 11C. The powderreplenishment device 13 is connected at its output end to the upstreamend powder supply unit 11A via a connection pipe 23. The powderreplenishment device 13 is connected at its input end to the downstreamend powder supply unit 11C via a connection pipe 35.

A suction unit 15 is provided in connection with the downstream endpowder supply unit 11C via the powder replenishment device 13. Thesuction unit 15 is for generating a suction force or negative pressureto supply powder to the powder supply units 11A to 11C and draw excesssupplied powder back to the powder replenishment device 13.

A powder collection device 37 for collecting residual powder suppliedfrom the powder supply units is disposed beneath the second stretcher 9.The powder replenishment device 13 is also connected to the powdercollection device 37 via a connection pipe 39. Further, the suction unit15 is also connected to the powder collection device 37.

The powder replenishment device 13 includes a holding body 17, aswitching valve 21, a switching valve 33, a cyclone classifier 29, and asieve device 25. Although not shown in the drawings, the holding body 17has an internal hopper for storing powder to be supplied. Also, arotatable pipe having a length corresponding to the length of the hopperrotatably extends in a horizontal direction at the bottom of the hopper.Suction ports or slits for sucking up powder from the hopper are formedin a spiral configuration in the rotatable pipe. A motor M1 is providedfor rotating the rotatable pipe. The arrangement of the hopper and therotatable pipe is disclosed in a co-pending U.S. patent application Ser.No. 08/789,128 disclosure of which is hereby incorporated by reference.

The switching valve 21 is connected to the rotatable pipe by aconnection pipe 19 and to the upstream end powder supply unit 11A by theconnection pipe 23. Said differently, the connection pipe 19 has one endconnected to the rotatable pipe in the hopper and another end connectedto the switching valve 21. The switching valve 21 is for switchingsupply from the powder replenishment device 13 between to the productionline of FIG. 1 and to another system (not shown).

The switching valve 33 is connected to the downstream side of theproduction line of FIG. 1, that is, to the downstream end powder supplyunit 11C, via the connection pipe 35, and also to the powder collectiondevice 37 via the connection pipe 39. The switching valve 33 can becontrolled to selectively switch connection of the powder replenishmentdevice 13 to either the downstream end powder supply unit 11C (theconnection pipe 35) or to the powder collection device 37 (theconnection pipe 39).

The cyclone classifier 29 and the sieve device 25 are provided forseparating the collected powder from any dough particles, or other solidmaterials collected with the powder from the production line beforereturning the collected powder back to the hopper in the powderreplenishment device 13. The cyclone classifier 29 is connected to theswitching valve 33 and to the suction unit 15. Said in more detail, thecyclone classifier 29 has an inlet port 31 connected to the switchingvalve 33. The cyclone classifier 29 has a discharge port 29P (FIG. 5)connected to a connection pipe 27, which is connected to the suctionunit 15. The sieve device 25 is disposed above and connected to thecyclone classifier 29. The sieve device 25 supplies the separated powderback to the hopper.

With this configuration, when the powder replenishment device 13 and thesuction unit 15 are driven to operate, powder supplied from the powderreplenishment device 13 is drawn by suction force generated at thesuction unit 15 and is supplied to the upstream end powder supply unit11A, to the middle powder supply unit 11B, and to the downstream endpowder supply unit 11C, one after another in this order. With thisconfiguration, powder can be supplied where needed without the powderbeing ejected out of the supply system and sprayed around the productionline. As a result, area around the production line can be maintained ina sanitary condition.

Next, the powder supply units 11A through 11C will be described withreference to FIGS. 2 through 4, using the powder supply unit 11A as arepresentative example. However, it should be noted that theconfiguration of all the powder supply units 11A through 11C arebasically the same.

The powder supply unit 11A generally includes an auxiliary tank 57, abox-shaped powder reservoir 45 disposed beneath the auxiliary tank 57for storing powder, and a powder supplying portion 47 disposed beneaththe reservoir 45 for supplying the powder to the processing device 1.

The auxiliary tank 57 has a relatively deep box shape and includes ashutter 55, which serves as the bottom of the box shape. The auxiliarytank 57 has an internal volume capable of performing a continuous powdersupply from the powder supplying portion 47 for ten minutes providedthat all powders in the auxiliary tank 57 are dropped into the powdersupplying portion 47. A lid 65 is detachably provided at the top of theauxiliary tank 57.

As shown in FIG. 3, an inlet conduit 67 for connecting to the powderreplenishment device 13 is disposed at one end of the upper portion ofthe auxiliary tank 57. An outlet conduit 69 for connecting to thesuction unit 15, that is, via the other powder supply units 11B and 11C,is disposed at the other end of the upper portion of the auxiliary tank57.

A support bar 71 is provided to the upper portion of the auxiliary tank57. The support bar 71 extends parallel to the direction in which powderis transported and spans from the inlet conduit 67 to the outlet conduit69. A plurality of partitions 73 for intentionally obstructing smoothflow of powder from the inlet conduit 67 to the outlet conduit 69 aredisposed along the support bar 71.

The partitions 73 are configured so that their positions on the supportbar 71 can be adjusted. That is, as shown in FIG. 4, the partitions 73according to the present embodiment are formed in a substantially Ushape. The partitions 73 are formed to develop an urging force thatresiliently spreads open the U-shaped portion. The support bar 71penetrates through the substantially U-shaped portion of each partition73. The urging force fixes the partitions 73 on the support bar 71.However, the user can move each partition 73 along the support bar 71 byslightly pinching closed the U-shaped portion against the urging forceof the U-shaped portion and then sliding the partition along the supportbar 71. Further, a relatively large space 75 is defined between theupper portion of the partitions 73 and the lid 65 for facilitating theflow of powders through the space 75. That is, even after one auxiliarytank is filled up, powder can be easily transported to the nextauxiliary tank.

A pivot shaft 56 is provided at the upper portion of the powderreservoir 45, and the shutter 55 is pivotally disposed on the shaft 56.Thus, the shutter 55 can pivot upward and downward to selectivelypartition the auxiliary tank 57 from the powder reservoir 45. While theshutter 55 is closed, powder accumulates in the auxiliary tank 57 byoperation of the partitions 73. Opening the shutter 55 releases theaccumulated powder into the powder reservoir 45.

A rotary actuator 59, a crank arm 61 and a pressing roller 63 areprovided for opening and closing the shutter 55. The rotary actuator 59is provided at the powder reservoir 45 and has a rotation shaft. Thecrank arm 61 has a free end rotatably provided with the pressing roller63, and another end attached to the rotation shaft. The pressing roller63 is disposed in abutment with the surface of the shutter 55. With thisconfiguration, the shutter 55 can open by its own weight, and can thenbe closed by appropriate pivotal movement of the crank arm 61.

The amount of powder in the powder reservoir 45 gradually decreasesbecause the powder supply portion 47 supplies powder in the powderreservoir 45 to a corresponding processing device. A level sensor 77 isprovided at a lower limit position in the powder reservoir 45 to detectwhen the amount of powder remaining in the powder reservoir 45 is at alower limit. When the level sensor 77 detects that the powder in thepowder reservoir 45 has dropped to the lower limit position, the rotaryactuator 59 is driven to open the shutter 55 so that powder in theauxiliary tank 57 drops into the powder reservoir 45.

The powder supply portion 47 is for supplying powder from the powderreservoir 45 to the corresponding stage in the production line. Thepowder supply portion 47 includes a casing 51, a cylindrical rotor 53,and a motor M2. The casing 51 is attached integrally to the bottom ofthe powder reservoir 45. A mesh 49 is provided as a bottom portion ofthe casing 51. The rotor 53 is rotatably provided in the casing 51. Therotor 53 is for moving the powder from inside the powder reservoir 45 tothe position of the mesh 49. The motor M2 is provided to the casing 51for rotating the rotor 53.

With the above-described configuration, when the suction unit 15 and thepowder replenishment device 13 are operated, powder supplied from thepowder replenishment device 13 is first sucked in through the inletconduit 67 into the auxiliary tank 57 of the upstream end powder supplyunit 11A. Powder introduced into the auxiliary tank 57 through the inletconduit 67 settles by its own weight and also abuts against thepartitions 73 within the auxiliary tank 57, whereupon further movementof the powder toward the outlet conduit 69 is obstructed by thepartitions 73. Accordingly, powder within the auxiliary tank 57gradually accumulates until the auxiliary tank 57 is filled.

When the auxiliary tank 57 of the upstream end powder supply unit 11Afills up with powder, further powder sucked into the auxiliary tank 57from the inlet conduit 67 passes through the space 75 between thepartitions 73 and the lid 65 and flows out through the outlet conduit69. As a result, the excess powder is sucked into the auxiliary tank 57of the middle powder supply unit 11B until the auxiliary tank 57 of themiddle powder supply unit 11B is filled. This process is also repeatedto fill up the auxiliary tank 57 of the downstream end powder supplyunit lC. When the auxiliary tanks 57 of all the powder supply unit 11A,11B, and 11C are filled with powder, then the excess powder will flowout from the outlet conduit 69 of the auxiliary tank 57 in thedownstream end powder supply unit 11C and enter the cyclone classifier29. The cyclone classifier 29 uses centrifugal force to separate powderfrom the air flow induced by the suction unit 15. The separated powderis then returned to the holding body 17 of powder replenishment device13 via the sieve device 25.

According to the configuration of the present embodiment, all of theauxiliary tanks 57 are filled from an empty condition in a few minutes.Therefore, it is desirable to stop drive of the suction unit 15 and thepowder replenishment device 13 once the auxiliary tanks 57 become fullof powder. To this effect, a powder detection device is provided in thecyclone classifier 29. The powder detection device is adapted fordetecting when the auxiliary tanks 57 of all the powder supply units 11Athrough 11C are filled with powder. Drive of the suction unit 15 and ofthe powder replenishment device 13 are stopped based on detection by thepowder detection device. In other words, the powder detection deviceserves as a powder sensor and means for stopping the operation of thereplenishment device 15 and the suction unit 15.

As shown in FIG. 5, the cyclone classifier 29 includes a conical bodyportion 79 at its lower end. A cylindrical portion 79a with a slantinglower surface is disposed in connection with the lower end of theconical portion 79. A substantially vertical opening 81 is formed in theleftward facing (as viewed in FIG. 5) side of the cylindrical portion79a. A first shutter 83 is swingably suspended adjacent to the opening81. The first shutter 83 is swingable between a closed position, whichcloses the opening 81, and an open position, which opens the opening 81.The first shutter 83 swings into its closed position by its own weightto close the opening 81.

An air chamber wall 85 is provided so as to surround the slantedcylindrical portion 79a and the opening 81. The air chamber wall 85 isin a slanted orientation with respect to the conical portion 79 of thecyclone classifier 29, and defines therein an air chamber space. Asubstantially vertical opening 87 is formed in the leftward facing (asviewed in FIG. 5) side of the air chamber wall 85. A second shutter 89is swingably suspended adjacent to the opening 87. The second shutter 89is swingable between a closed position, which closes the opening 87, andan open position, which opens the opening 87. The second shutter 89swings into its closed position by its own weight to close the opening87. The opening 87 is fluidly connected to the sieve device 25 of thepower replenishment device 13 when the second shutter 89 is opened.Further, a sensor 90 is disposed adjacent to the second shutter 89 fordetecting opening movement of the second shutter 89. When the sensor 90detects the opening movement, the operation of the powder replenishmentdevice 13 and the suction unit 15 are stopped.

A pressure switching valve 91 is connected to the air chamber wall 85.The pressure switching valve 91 includes an atmosphere inlet port 93Pand another inlet port connected to the discharge port 29P of thecyclone classifier 29 by a bypass pipe 93. An actuator 95 is providedfor operating the pressure switching valve 91 to connect the air chamberspace alternately with the bypass pipe 93 and the atmosphere inlet port93P. The pressure switching valve 91 is operated each time apredetermined duration of time, such as a few seconds, elapses asdetermined by, for example, a timer.

The first shutter 83 is urged to its closed position by its own weightand by suction force of the suction unit 15 if the air chamber 85 isconnected with the atmosphere inlet port 93P. That is, to close thefirst shutter 83 tight by suction force of the suction unit 15, thepressure switching valve 91 is operated to connect the air chamber 85with the outside atmosphere through the atmosphere inlet port 93P. Thefirst shutter 83 will close tight because the pressure on the airchamber side of the first shutter 83 will be higher than on the cycloneclassifier side. As a result, when all powder supply units 11A to 11Cbecome full of powder so that powder flows out of the auxiliary tank 57of the downstream end powder supply unit 11C and into the cycloneclassifier 29, the powder will accumulate in the cyclone classifier 29at a position adjacent to the opening portion 81.

To maintain the closed position of the first shutter 83 merely by theweight of the first shutter 83, the pressure switching valve 91 isoperated to connect the air chamber 85 with the suction unit 15 throughthe bypass pipe 93 and the connection pipe 27. As a result, the pressureat both inner and outer sides of the first shutter 83 will be inequilibrium so that the first shutter 83 is closed by its own weightonly. If powder has accumulated in the cyclone classifier 29 at thistime, the first shutter 83 will be opened by weight of the accumulatedpowder so that the accumulated powder drops into the air chamber 85.

When the pressure switching valve 91 is operated to connect the airchamber 85 with atmosphere, so that the first shutter 83 closes tight,the air chamber 85 will be disconnected from the suction unit 15. As aresult, pressure at both inner and outer surfaces of the second shutter89 will equalize so that the second shutter 89 will be closed only byits self weight. Therefore, when powder drops out of the cycloneclassifier 29 by opening of the first shutter 83 and accumulates in theair chamber 85, the second shutter 89 will be opened up by weight of thepowder.

In other words, when all powder supply units 11A to 11C become full ofpowder so that powder flows out of the auxiliary tank 57 of thedownstream end powder supply unit 11C and into the air chamber 85, thepowder in the air chamber 85 will open up the second shutter 89 when thepressure switching valve 91 is operated to connect the air chamber 85with atmosphere. Because the sensor 90 detects when the second shutter89 opens, it can detect when all the powder supply units 11A to 11C arefull. Operation of the powder replenishment device 13 and the suctionunit 15 are stopped in response to the detection signal from the sensor90, i.e., when the sensor 90 detects that the second shutter 89 opens.

On the other hand, when pressure switching valve 91 is operated toconnect the air chamber 85 to the suction unit 15 through the bypasspipe 93, a negative pressure develops in the air chamber 85. The secondshutter 89 shuts closed tight because of higher pressure the outer sideof the second shutter 89. In this case, powder will not drop out of theair chamber 85, even if powder has accumulated adjacent to the secondshutter 89. Since powders to be detected is confined in the air chamberwall 85, whether the auxiliary tanks have each been filled up can bedetected without any problem even if powder floats upward when beingdrop down.

With the above described configuration, first the auxiliary tanks 57 ofall of the powder supply units 11A to 11C are filled up with powder.While the powder is supplied from the powder supplying portion 47 of oneof the powder supply units to the corresponding processing device in theproduction line, the amount of powder in the powder reservoir 45 of oneof the powder supply units gradually decreases. When the amount ofpowder in the particular powder supply unit decreases to the level ofthe level sensor 77, the level sensor 77 will detect that the amount ofpowder has decreased to the lower limit, whereupon the rotary actuator59 is operated to open the shutter 55 so that powder accumulated in theauxiliary tank 57 falls into the powder reservoir 45.

When a predetermined duration time elapses after the shutter 55 opensup, the rotary actuator 59 operates in reverse to close the shutter 55.When the shutter 55 closes, the powder replenishment device 13 and thesuction unit 15 are again driven to replenish powder into the emptyauxiliary tank 57 or tanks.

Accordingly, the auxiliary tank 57 of all the powder supply units 11A to11C can be maintained in a filled condition. Therefore, powder can bepromptly supplied from the auxiliary tank 57 into the powder reservoir45 in accordance with reduction of powder in the powder reservoir 45.

In this way, according to the first embodiment of the present invention,the powder supply units are connected in series and the suctionoperation of the suction device sucks powder into auxiliary tanks tofill the auxiliary tanks of the powder supply units one at a time inorder starting from the upstream end auxiliary tank. Therefore, there isno need to provide branch piping or switching valves to switch betweendifferent pipes of the branch piping. Thus, configuration of piping issimplified. Further, because powder is transported by a suctionoperation, the powder will not be blown around so that area around thesystem can be maintained in a more sanitary condition.

The embodiment discloses a configuration for supplying powder bydropping powder from the auxiliary tank 57 down into the powderreservoir 45. The shutter 55 is operated to open when the level sensor77 detects that the amount of powder in the powder reservoir 45 hasreduced to a lower limit. According to the present embodiment, powdercan be supplied to completely fill all the auxiliary tanks 57 in amatter of minutes. However, the powder in the powder reservoirs 45 canbe supplied by the corresponding powder supplying portions 47 forseveral tens of minutes before the amount of powder in the powderreservoirs 45 decreases to the lower limit as detected by the levelsensors 77. For this reason, the powder supply units 11A to 11C can beconfigured so that all the shutters 55 of all the powder supply units11A to 11C are operated simultaneously every several tens of minutes.This can be achieved by providing a valve opening control device using atimer to control the shutter 55 to open each time a predetermined timeset by the timer elapses. Thus, powder can be supplied to the powderreservoir 45 each time a predetermined duration of time elapses, so thatshortages of powder in the powder reservoir 45 can be prevented.

Even if the amount of powder held in different powder reservoirs 45decreases at different rates, the reduced amount in each will bereplenished when the corresponding shutter 55 is operated to open. Theauxiliary tanks 57 of the powder supply units 11A to 11C are filled upin order from the upstream end powder supply unit 11A to the downstreamend powder supply unit 11C. Therefore, there is no problem in fillingpowder into each auxiliary tank 57.

Next, a powder supply unit 111 according to a second embodiment of thepresent invention will be described while referring to FIGS. 6 and 7. Toavoid duplication of the description, the powder supply unit 111 of thesecond embodiment will be described wherein like parts and componentsare designated by the same reference numerals as the powder supply units11A to 11C of the first embodiment.

The powder supply unit 111 has a powder supplying portion 47 disposed toextend in a direction that intersects the direction in which powder istransported. That is, the powder supplying portion 47 extends in adirection that intersects the direction in which the inlet conduit 67and the outlet conduit 69 are aligned to connect to the auxiliary tank57. In the second embodiment, the powder supplying portion 47 isdisposed perpendicular to the direction in which powder is transported.A pair of screw conveyers 101A, 101B are rotatably disposed above therotor 53 in the powder supplying portion 47. The pair of screw conveyers101A, 101B are provided for transporting powder in the powder reservoir45 to above the rotor 53.

Even though both the pair of screw conveyers 101A, 101B can beconfigured to also transport powder in the powder reservoir 45 up abovethe rotor 53, one of the screw conveyers can be configured to transportpowder in the powder reservoir 45 above the rotor 53 and the other screwconveyer can be configured to transport powder in the reverse directionso that powder is distributed evenly. Further, in order to preventarching phenomenon, that is, non-uniform deposition, in the powderwithin the powder reservoir 45, a swinging or vibrating lattice-shapedoscillating member 103 is provided internally in the powder reservoir 45111 for vibrating the powder.

The powder supply unit 111 according to the second embodiment isadvantageous when the positioning of the surrounding equipment does notenable aligning the lengthwise directions of the auxiliary tank 57 andthe powder supplying portion 47.

While the invention has been described in detail and with reference tothe specific embodiments thereof, it would be apparent to those skilledin the art that various changes and modifications may be made thereinwithout departing from the spirit and scope of the invention.

For example, in the above described embodiment, the powder detectiondevice is provided in the cyclone classifier 29. However, it should benoted that the powder detection device can alternatively be providedanywhere between the auxiliary tank 57 of the downstream end powdersupply unit 11c and the suction unit 15 in order to detect outflow ofpowder from the downstream end powder supply unit lC. For example, thepowder detection device could be provided to a portion of the connectionpipe 35 or at the outlet port 69 of the auxiliary tank 57 in thedownstream end powder supply unit 11C.

Further, the above-described embodiment describes detecting when all thepowder supply units 11A to 11C become full of powder, by using thesensor 90 to detect opening operation of the second shutter 89. However,whether all the powder supply units 11A to 11C are full could bedetected based on opening and closing of the first shutter 83 instead.Further, whether all the powder supply units 11A to 11C are full couldbe detected using a variety of configurations for detecting when powderaccumulates at the opening portions 81, 87. For example, a configurationprovided with a switch operating by weight of the accumulated powder ora configuration for optically detecting the accumulated powder could beused.

Further, in the above-described embodiments, the inlet conduits 67 andthe outlet conduits 69 are disposed in connection with the auxiliarytank 57 substantially aligned on the same imaginary axis so that flow ofthe powder is substantially linear. However, the inlet conduit and theoutlet conduit need not be disposed aligned on the same imaginary axis.For example, the inlet conduit and the outlet conduit need only bedisposed near the lengthwise ends of the auxiliary tank without concernfor directionality of the inlet conduit with respect to the outletconduit. That is, the inlet conduit and the outlet conduit can bedisposed to guide flow of powder to backtrack in a U-turn fashion or toturn left or right following L-shaped bends.

Also, the partitions 73 need not be provided, although they aredesirably provided to assist in uniformly accumulating the powder withinthe auxiliary tank 57.

What is claimed is:
 1. A powder supply system for supplying powders to aplurality of processing devices comprising:a powder replenishment devicestoring therein powders; a powder suction device for suckinglydischarging the powders in the powder replenishment device; a pluralityof powder supply units connected in series and positioned between thepowder replenishment device and the powder suction device, andcomprising an upstream end powder supply unit, and a downstream endpowder supply unit, each powder supply unit being provided for supplyingpowders to each processing device, and each powder supply unitcomprising: an auxiliary tank for temporarily storing therein thepowders, the auxiliary tank having an upper portion and a lower portion;a powder inlet conduit connected to the upper portion of the auxiliarytank for introducing powders into the auxiliary tank; a powder outletconduit connected to the upper portion of the auxiliary tank fordischarging the powders from the auxiliary tank; and a powder supplyingportion provided at the lower portion of the auxiliary tank forsupplying the powders conveyed from the auxiliary tank to eachprocessing device, the inlet conduit of the upstream end auxiliary tankbeing connected to the powder replenishment device and the outletconduit of the downstream end auxiliary tank being connected to thepowder suction device, the powder suction device sucking the powders inthe powder replenishment device through the inlet conduits and theoutlet conduits and through the respective auxiliary tanks forsuccessively and fully accumulating powders in the auxiliary tanks inthe order from the upstream end auxiliary tank to the downstream endauxiliary tank; and a powder sensor connected to a downstream of thedownstream end powder supply unit for detecting a full accumulation ofthe powders in all auxiliary tanks and for stopping operation of thepowder replenishment device and the powder suction device as a result ofthe powder detection.
 2. A powder supply system as claimed in claim 1,wherein each of the powder supply units further comprises a powderreservoir provided immediately below the auxiliary tank and immediatelyabove the powder supplying portion;and wherein the lower portion of theauxiliary tank is provided with a valve movable between a close positionfor accumulating the powders in the auxiliary tank and an open positionfor dropping the powders in the auxiliary tank into the powderreservoir.
 3. The powder supply system as claimed in claim 2, whereinthe powder sensor is provided at a position between the downstream endpowder supply unit and the powder suction device for detecting thepowders flowed from the outlet conduit of the downstream end powdersupply unit.
 4. The powder supply system as claimed in claim 3, furthercomprising a cyclone classifier provided at a fluid passage between thedownstream end powder supply unit and the powder suction device forseparating the powders from a suction air, the powder detection devicedetecting the powders separated by the cyclone classifier.
 5. The powdersupply system as claimed in claim 4, wherein the cyclone classifier isfluidly connected to the powder replenishment device for returning thepowders separated by the cyclone classifier into the powderreplenishment device.
 6. The powder supply system as claimed in claim 5,wherein the cyclone classifier comprises:a conical body portion having alower opening; an air chamber wall surrounding the lower opening andconnected to the power replenishment device, the air chamber walldefining therein an air chamber space; a first shutter provided to thelower opening and movable between an open position for opening the loweropening and a close position for closing the lower opening; a secondshutter provided to the air chamber wall, the second shutter opening orclosing the air chamber space in accordance with flow of the powdersthrough the air chamber wall, the air chamber space being incommunication with the powder replenishment device when the secondshutter is opened; and a pressure change-over valve connected to the airchamber space for selectively communicating the air chamber space withone of the powder suction device and an atmosphere.
 7. The powder supplysystem as claimed in claim 6, wherein the powder sensor is provided atthe air chamber wall for detecting opening movement the second shutter.8. The powder supply system as claimed in claim 2, further comprisingmeans for starting operation of the powder replenishment device and thepowder suction device in response to the closing movement of the valve.9. The powder supply system as claimed in claim 2, wherein the powderinlet conduits and the powder outlet conduits are arrayed in line in onedirection, and the powder supplying portion extends in a direction thatintersects the one direction;and wherein each of the powder supply unitsfurther comprises a conveyer disposed over the powder supplying portionfor conveying powders from a bottom portion of the powder reservoir tothe powder supplying portion.
 10. The powder supply system as claimed inclaim 9, wherein the conveyer comprises a first screw conveyer forfeeding the powder in a first direction and a second screw conveyerextending in parallel with the first screw conveyer for feeding thepowder in a second direction opposite to the first direction.
 11. Thepowder supply system as claimed in claim 1, wherein the powder inletconduits and the powder outlet conduits are arrayed in line in onedirection, and the system further comprising a plurality of partitionplates disposed in the auxiliary tank and arrayed in the one directionand spaced away from each other for obstructing a smooth flow of powdersflowing through the auxiliary tank.
 12. The powder supply system asclaimed in claim 11, wherein the auxiliary tank has a top wall, the topwall and the partition plates defining a space therebetween forpermitting the powders to flow through the space even after theauxiliary tank is filled with powders.
 13. The powder supply system asclaimed in claim 2, further comprising a level sensor disposed in thepowder reservoir for detecting a lower limit level of the powders in thepowder reservoir.
 14. The powder supply system as claimed in claim 2,further comprising means for controlling opening and closing movement ofthe valve at an every predetermined time interval.